High-pressure pump and fuel-supply system using same

Abstract

A high-pressure pump includes: a low-pressure chamber, into which low-pressure fuel discharged from a low-pressure pump flows; a pressurizing chamber, which pressurizes the low-low-pressure fuel; and a leak chamber, into which leaked fuel from the pressurizing chamber flows. The leaked fuel of the leak chamber is suctioned into and is pressurized in the pressurizing chamber together with the low-pressure fuel of the low-pressure chamber, so that the leaked fuel is discharged to an outside of the high-pressure pump as high-pressure fuel. Furthermore, a suction check valve, which is placed between the low-pressure chamber and the leak chamber, limits backflow of the leaked fuel of the leak chamber to the low-pressure chamber when the high-pressure pump does not supply the high-pressure fuel.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is based on and incorporates herein by reference Japanese Patent Application No. 2014-246992 filed on Dec. 5, 2014.TECHNICAL FIELD[0002]The present disclosure relates to a high-pressure pump and a fuel-supply system using the same.BACKGROUND ART[0003]Previously, there is known a fuel-supply system that can supply fuel of different pressures to an internal combustion engine. For example, the patent literature 1 recites a fuel-supply system that includes: a low-pressure pump that pressurizes fuel of a fuel tank to a relatively low pressure and discharges the pressurized fuel; a high-pressure pump that pressurizes the fuel pressurized by the low-pressure pump to a relatively high pressure and discharges the pressurized fuel; a low-pressure fuel injection valve that injects the low-pressure fuel discharged from the low-pressure pump; and a high-pressure fuel injection valve that injects the high-pressure fuel discharged from t...

AI Technical Summary

Benefits of technology

[0007]It is an objective of the present disclosure to provide a high-pressure pump that can limit seizing of a plunger. It is another objective of the present disclosure to provide a fuel-supply system that includes the above high-pressure pump.

[0014]In the high-pressure pump of the present disclosure, the fuel of the fuel tank is suctioned into the pressurizing chamber through the inlet port, the leak chamber and the suction flow passage. The fuel, which is suctioned into the pressurizing chamber, is pressurized by the plunger and is discharged to an outside of the high-pressure pump. Thereby, when the high-pressure pump discharges the fuel of the high-pressure, the leaked fuel in the leak chamber is reliably discharged to the outside of the high-pressure pump through the suction flow passage, the pressurizing chamber and the outlet port together with the fuel of the fuel tank, which is introduced from the inlet port. In this way, it is possible to limit an increase of the temperature of the high-pressure pump, which is caused by long stay of the leaked fuel having the high temperature in the leak chamber, and thereby it is possible to limit evaporation of the fuel that is located between an inner wall of the pressurizing portion, which slides along an outer wall of the plunger, and the outer wall of the plunger.

[0015]Furthermore, the fuel stays in the leak chamber, the suction flow passage and the pressurizing chamber when the high-pressure pump is not discharging the fuel of the high pressure, i.e., when the discharging of the leaked fuel is not executed. When the temperature of the high-pressure pump is increased by the environment, in which the high-pressure pump is placed, the temperature of the fuel, which stays in the leak chamber, is increased. In the high-pressure pump of the present disclosure, the fuel can be supplied from the inlet port to the leak chamber by the suction check valve, but the fuel cannot be returned from the leak chamber to the inlet port. Therefore, the pressure of the fuel in the leak chamber is not excessively reduced, and thereby the fuel in, for example, the leak chamber is not evaporated. In this way, it is possible to limit the evaporation of the fuel, which is located in the gap between the inner wall of the pressurizing portion and the outer wall of the plunger, by the temperature increase of the high-pressure pump when the high-pressure pump is not discharging the fuel of the high pressure.

[0016]As discussed above, in the high-pressure pump of the present disclosure, the evaporation of the fuel, which is located in the gap between the inner wall of the pressurizing portion and the outer wall of the plunger, is limited regardless of whether the high-pressure pump is discharging the fuel of the high pressure. Thus, the smooth slide movement between the pressurizing portion and the plunger is ensured, and thereby the seizing of the plunger can be limited.

Problems solved by technology

Therefore, when the leaked fuel leaks into a space having a relatively low pressure, the temperature of the leaked fuel becomes high.

When this leaked fuel stays in this space for a relatively long period of time, the temperature of the high-pressure pump becomes high.

However, when the fuel in the gap is evaporated to form the fuel vapor, the smooth slide movement between the housing and the plunger becomes difficult.

Therefore, seizing may possibly occur between the inner wall of the housing and the outer wall of the plunger to possibly cause a damage of the high-pressure pump.

However, there are some disadvantages, such as an increase in the number of pipes for returning the leaked fuel and a difficulty of providing a space for installing these pipes depending on an install location of the high-pressure pump.

However, all of the leaked fuel cannot be discharged to the outside of the high-pressure pump, so that there is a possibility of that the temperature of the high-pressure pump is increased.

However, the temperature and the pressure of the fuel supplied to the low-pressure fuel injection valve may be changed by the temperature and the pressure of the leaked fuel.

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